A Pakistani official says gunmen have opened fire on a NATO supply convoy in the country’s northwest, killing two truck drivers and wounding another.

Local administrator Mohammed Asif says the attack took place in the tribal Jamrud region on Tuesday when the trucks were heading to neighboring Afghanistan to take supplies to NATO forces.

Jamrud is located 40 kilometers (25 miles) northwest of the city of Peshawar.

The attack comes less than a week after the ruling political party in the northwest ended a three-month blockade of a NATO supply route to Afghanistan over contentious U.S. drone strikes in the country.